UA3457 is used on multiple routes. Typically, UA3457 flies straight from Pittsburgh, PA (PIT-Pittsburgh Intl.) to Chicago, IL (ORD-O'Hare Intl.). If that's your flight path, you'll be in the air for approximately 1 hour and 34 minutes.
It's possible you'll be setting off on an Embraer 170 if you're flying from Pittsburgh, PA (PIT-Pittsburgh Intl.) to Chicago, IL (ORD-O'Hare Intl.), one of several routes used for flight number UA3457.